Luminous Landscape Forum

Equipment & Techniques => Medium Format / Film / Digital Backs – and Large Sensor Photography => Topic started by: skimasks on August 28, 2010, 01:10:46 am

Title: Maze/mosaic patterns in Phase One files
Post by: skimasks on August 28, 2010, 01:10:46 am

I just shot a few shots with my new/used P25+ and I noticed there were light leaks in my bellows (I am shooting it attached to a horseman view camera with a 210mm caltar lens. When opening the files on my computer (in PS CS3) I found that there were maze shaped patterns on the image, especially where the light leak occurred. I had seen this before with one of sony's dslrs but never on a digital back. When opening the same file in Capture One Pro it seems the file's mosaic pattern either was
a) not there anymore
b) was smoothed over/affected by slight posterization.

Does anyone know what causes this/where I could find out more about the pattern, what causes it, how to remedy?

Title: Re: Maze/mosaic patterns in Phase One files
Post by: ondebanks on August 28, 2010, 07:30:56 pm

Welcome to the forum, ski' !

Could you post an image of the problem? Might help us to diagnose it.

Title: Re: Maze/mosaic patterns in Phase One files
Post by: skimasks on August 28, 2010, 08:16:33 pm

Sure thing
this is a 400 percent blowup.
(http://i89.photobucket.com/albums/k225/skimasks/CF016196ACR.jpg)

Title: Re: Maze/mosaic patterns in Phase One files
Post by: Doug Peterson on August 28, 2010, 09:53:33 pm

This looks similar to "pattern noise" caused by having an extreme highlight somewhere within the image.

Capture One automatically corrects for it with minimal artifacts of the process of removal.

Title: Re: Maze/mosaic patterns in Phase One files
Post by: ondebanks on August 29, 2010, 08:22:08 am

Hmm. That doesn't look like any pattern noise I've ever seen from a CCD. What's the underlying physical cause of the "maziness", Doug?

Title: Re: Maze/mosaic patterns in Phase One files
Post by: deejjjaaaa on August 29, 2010, 09:46:45 am

Quote from: ondebanks on August 29, 2010, 08:22:08 am

That doesn't look like any pattern noise

this maze pattern is a demosaicing bug.

Title: Re: Maze/mosaic patterns in Phase One files
Post by: Graeme Nattress on August 29, 2010, 09:49:55 am

Yes, it's a demosaicing artifact where the algorithm has difficulty coping with edge interpolation on flat, but slightly noisy areas, getting confused and producing a maze-like pattern. It sounds like better raw software is needed for these images - one with a more advanced demosaicing algorithm.

Graeme

Title: Re: Maze/mosaic patterns in Phase One files
Post by: skimasks on August 29, 2010, 04:36:59 pm

Thanks guys, this gives me a solid jumping off ground for researching how/why this happens! I'll just have to update my ACR..or just use C1Pro to process before post production.

I didn't realize you posted here Graeme, I usually read your posts on Red User. :)

Title: Re: Maze/mosaic patterns in Phase One files
Post by: Graeme Nattress on August 29, 2010, 05:13:22 pm

I think I was posting here before REDUser even existed.... :-)

Graeme